1. Field of the Invention
The present invention relates to a navigation system for detecting the position of a moving body to inform a user of the current position of the moving body, and a map display apparatus using the navigation system.
2. Description of Related Art
Various types of navigation systems have been recently known, and these navigation systems are used while mounted on moving bodies such as vehicles, ships, etc. When such a navigation system is mounted on a moving body, it performs arithmetic and logic processing on information provided from various sensors to detect the current position of the moving body and display the current position on a screen of the navigation system.
This type of navigation system includes a position detector for detecting the absolute position of the moving body, a storage device for storing map data which include two-dimensional vector data obtained by projecting roads and points on the ground, such as structures, etc., onto a mesh-segmented plane using a universal transverse Mercator projection method, and character data associated with the vector data, an input device for receiving external instructions (commands), and a display device for reading out desired vector data from the mesh-segmented map stored in the storage device in accordance with an instruction input from the input device, to perform data conversion processing on the data, and then displaying the map on the display.
The data conversion processing includes shift conversion processing for changing the display position on a map, scale conversion (enlarging/reducing) processing for displaying a map on any scale, and rotational coordinate-transformation processing for changing a display direction on the map. With these processings, a plan view map is obtained by drawing the ground through an orthogonal projection in a vertical direction.
As described above, when a map is displayed on the screen, the conventional navigation system as described above adopts a plan-map display mode in which the ground is drawn in the vertical orthogonal projection style. Therefore, in order to simultaneously display two spots which are far away from each other, a reduction-scale of the map must be necessarily increased, and thus detailed information cannot be displayed on the screen.